Furnace construction



July l, 1930.

E. J. McDoNNELL 1,769,446

FURNACE CONSTRUCTION Filed Ilay 16 1921 2 Sheets-Sheet 1 July l, 1930. E. J. McDoNNELL FURNACE CONSTRUCTION Filed May 16 1921 2 Sheets-Sheet 2 Patented July 1, 1930 EDWARD J'. MUDONNELL, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO OPEN HEARTH A CORPORATION OF DELAWARE COMBUSTION COMPANY, OF CHICAGO, ILLINOIS,

FURNACE CONSTRUCTION Application led May 16,

This invention relates to a new and improved open hearth furnace, and more particularly to a construction of the air and gas ports of such a furnace especially adapted to so introduce the gases and air as to produce a quick-burning flame, and further so constructed as to maintain the ports of constant area.

In open hearth practice, as is well known, the furnace is provided with two ends which are duplicates of each other, and with duplicate regenerating chambers. In its operation it is reversed so that each end serves alternately as an incoming and as an outgoing end.

It is highly desirable to so intermingle the gas and air as to cause a quick flamethat is, a flame which begins substantially at the incoming ports. The air and gas are preheated in the regenerating chambers so that they enter through the ports at a high temperature, but this temperature of itself is not sufiiciently high to effect the proper working of the metal in the furnace. It is essential therefore that the combustion take place adjacent the port, for otherwise there is an area of the metal bath which is not worked, and the eliiciency of the furnace is thus impaired.

A further reason for the desirability of a. quick flame lies in the fact that the heated gases tend to wear away the ports on the outgoing end of the furnace. This erosion is much increased where the flame extends to or through these ports. It has heretofore been customary in many furnaces to pro- Vide the gas ports with water-cooling means which serve to preserve these ports against distortion or wearing away, and also to maintain their effective area constant. However, the wearing away of the walls surrounding the air ports gradually enlarges these ports and thus increases the quantity of air relative to the quantity of gas. Further, this wearing away of the air ports ,tends to vary the direction given the air flow, so that if the ports in a new furnace properly direct the air, when the furnace is toward the end of its useful life the 1921. Serial No. 469,859.

air is improperly directed for the purpose of securing the correct flame.

In furnaces of certain types, as for example that covered by the patent to Mc- Kune, No. 1,339,855, open hearth furnaces, issued May l1, 1920, additional ports are provided which are normally used only for the purpose of leading olf the products of combustion; that is, they are nf rmally opened only on the outgoing end of the furnace and are closed by valves on the incoming end. In such furnaces the incoming air and gas ports are relieved of a certain amount of the erosion caused by the heated outgoing gases, but are still subject to some wear from these gases and are of course also subject to wear from the incoming air and gas.

It is an object of the present invention to provide a new and improved open hearth furnace port construction wherein the air and gas are brought together and min led in a mixing chamber in order to pro uce a quick combustion, and further wherein water cooling means are provided in the walls of said ports and chamber adapted to maintain their area constant.

It is also an object to provide such means o located that a water cooling element in the gas port serves to define not only that port but a portion of the perimeter of the air port.

It is an additional object to provide water cooling means in the walls of the air port and defining its area, this water cooling element being provided at the points of minimum area of the port, and to provide similar means defining the mixing chamber.

It is a further object to provide such means in combination with additional lateral ports serving for the discharge of part of the products of combustion.

Other and further objects will the description proceeds.

Broadly, my invention comprises a gas port and associated air port, the air port walls preferably extending in advance of the gas port and forming a mixing chamber. The gas port and the adjacent walls of the air port are provided with water appear as cooling chambers, these chambers having portions extending to the surface of the walls and serving to define and limit their areas. Similar water cooling means are provided in the walls of the mixing chamber.

I have illustrated a preferred embodiment of my invention in the accompanying drawings, in which- Figure 1 is a plan view of a part of an open hearth furnace constructed according to my invention;

Figure 2 is a section on line 2-2 of Figure 1;

Figure 3 is a section on line 3--3 of Figure 1; and

Figure 4 is a Figure 1.

1t is to be understood that the open hearth furnace is provided with the usual regenerative chambers and air and gas passages of any ordinary construction, these elements forming no part of the present invention.

As shown in the drawings, the air uptakes 6 meet at 7, extending across above the gas port 8. The brickwork piers 9 serve to laterally guide the entering air, and as shown in Figure 3, these piers are joined by an arch 1() so that the air port is of an arched or horseshoe shape similar to, but larger than, the gas port 8 and surrounding that port.

The passageways 11 extend from the head of each uptake 6 to the melting chamber 12. These passages are controlled by vertically operated valves or dampers 13 which comprise a water chamber 14 and facing 15 of fire clay or similar material. The valves ride in water cooled guideways or seats 16 and are enclosed in the upper position by a hood 17 through which the stem 18 passes. This stem is hollow and serves to admit and withdraw the cooling water for the valve.

The gas uptake 19 leads to the gas port 8 and the latter port has its discharge end surrounded by the water cooling chamber 20. The outer end of this chamber 2O is broadened at 21 so that it serves to define not only the area of the gas port itself but also the outer area of the gas port structure. The water cooling chamber 22 is built in the walls of the piers 9 and arch 10 and completely encircles the air port. This chamber 22 is provided with a portion 23 which serves to define the outer perimeter of the air ort in substantially the plane of the end o the gas port. As shown in .the drawing, the mixing chamber 24 which is immediately beyond the end of the gas port gradually decreases in area to the point 25 which is defined by a portion 26 of the water cooling member 22.' Beyond the point 25 the mixing chamber as shown is of uniform area.

In the use of a furnace constructed aesection on line 4-4 of cording to my invention, normally the valves 13 will be in the lower position upon the incoming end of the furnace. Air will come up the uptakes, and being prevented by the valves from going through the passages 11, will be forced through the air passage efined by the gas port structure and the piers 9 and arch 10. The angle of these piers and arch is such as to direct the air against the sides and top of the incoming stream of gas and at such an an le to that stream as to facilitate intermingling of the air and gas.

It will be noted that no air is provided upon the lower side of the gas stream. This is not necesary, however, since the oras being lighter than the air tends to rise through the air and a mixture is therefore better afforded without a lower layer of air. The cooling members 20 and 22 serve to positively define the area both of the gas port and of the straddling air port. The port areas thus remain constant throu hout the life of these members and a uni orm and properly directed incoming air and gas stream is secured during the life of the furnace.

Tpon the outgoing ends of the furnace the valves 13 are raised so that the products of combustion pass out through the passages 11 and down through the air uptakes 6, to the usual regenerative chambers. These products also pass through the mixing chamber 24 and gas port 8 and down through the gas uptake 19, and through the mixing chamber and incoming air ports to the passages 11. These discharged gases are at a much higher temperature than the incoming gases and the cooling elements are particularly effective at this time in. maintaining the area and contour of the ports and preventing erosion at the critical points.

It is to be understood that under certain circumstances it may be found advisable or desirable to partly raise the valves 13 upon the incoming side of the furnace and to permit additional air to come through the passages 11 on that side of the furnace.

My particular port construction serves to adequately mix and properly direct the air and gas so as to cause a quick-burning fiame, partial combustion taking place in the mouth of the mixing chamber 24. This quick flame has the effect of minimizing erosion on the outgoing end of the furnace, and that erosion is further prevented by the water cooling elements which are provided for that purpose. These water cooling elements define not only the gas port as is now customary, but also the air port, and the mixing chamber and port through which both gas and air enter the furnace.

It is to be understood that the air and gas may be moved simply by the usual stack draft or may be moved by suction blowers located in the outgoing passages or by forced draft blowers. Either or both gas and air may be so handled on the incoming end, Normally, however, the air only will be forced through the This forced draft is somewhat restricted airinlet port and aids in mingling the air and gas for quick combustion. However, the contours of the passages adjacent the air port, of the port itself, and of the mixing chamber, have been so designed as to minimize the draft necessary.

I claim:

1. In an open hearth furnace, a gas port, an air port associated with the gas port, the outer walls of the gas port forming one wall of the air port, and water cooling means in said walls and in the adjacent air port walls at the point where said walls define the minimum cross sectional area of the air port.

2. In an open hearth furnace, a gas port, an air port associated with the gas port, the Walls of the air port extendinginwardly beyond the Walls of thegas port, and Water cooling means in said air port walls defining the inner line of said walls, said means being located substantially in the plane of the end of the gas port walls.

3. In an open hearth furnace, a gas port, an air port associated with the gas port, the walls of the air port extending inwardly beyond the walls of the gas port, and water cooling means in said air port walls defining the inner line of said walls, said means being located substantially in the plane of the end of the gas port Walls, said end of the gas port walls being defined by a water cooled element contained therein, whereby the area of said ports is maintained constant. l

4. In an open hearth furnace, a gas port, an air port associated with the gas port,- the walls of the air port extending inwardly beV yond the walls of the gas port to form a mixing port, and being inclined in such manner thatthe minimum area of the air port occurs substantially in the plane of the end of the gas port, and water cooling means in said air port walls in said plane.

5. In Van open hearth furnace, a gas port, an air port associated with the .gas port, the walls of the air port extending inwardly beyond the walls of the gas port to form a mixing port, the mixingport varying in area, and water cooling means defining the walls of said port at the point of least area whereby the area of the port is maintained substantially constant.

6. In an open hearth furnace, a gas port, an air port associated with the gas port, the walls of the air port extending inwardly beyond the walls of the gas port to form a mixing port, water cooling means in said air port Walls defining the inner line of said walls, saidf means being located subuptakes by a blower. desirable inview of the .tially in the stantially in the plane of the end of the gas port walls, the mixing port varying in area, and water cooling means defining the Walls of said port at the point of least area whereby the area of the port is maintained substantially constant.

K 7. In an open hearth furnace, a gas port, an air port associated with thegas port, the walls of the air port extending inwardly beyond the walls of the gas port to form a mixing port, water coollng means in said air port walls defining the inner line of said` walls, said means being located substanplane of the end of the' gas port walls, said end of the gas'port walls bein defined by a water cooled element contained therein whereby the areaof said ports is maintained constant, the mixing port varying in area, and water cooling means defining the Walls of said port at the point of least area whereby the area ofthe port is maintained substantially constant.

8. In an open hearth furnace, air and gas ports leading to a mixing port, said air and mixing ports being of varying area, and water cooling means located in the walls of said ports at the points of minimum area and serving to define the ports at these points whereby the area of said ports is maintained constant.

9. In an open hearth furnace, ports leading to a mixing port, and water cooling means located in the walls of the air and gas' ports at their point of discharge into the mixing port and serving to define the areas of the port-s. at said points.

10. In an open hearth furnace, air and gas ports leading to a mixing port, and water cooling means located in the walls of the air and gas ports at their point of discharge into the mixing port and serving to define the areas of the port at said points, the air port being located adjacent the 'gas port and the Water cooling means in the gas port walls servin both to define the area. of the gas port an of the adjacent perimeter of the air port.

11. In an open hearth furnace, a gas port, and an air entrance port, said air entrance port straddling the gas port, water cooling means in the gas port wall defining both inv. ner and outer faces of said Wall, and Water cooling means in the wall of the air port substantially opposite the first mentioned water cooling means whereby `the area of the air port is maintained constant.

12. In an open hearth furnace, air and gas ports leading to a mixing port, said air and mixing ports being of varying area, water cooling means located in the Walls of said ports at the points of .minimum area and serving to define ,the ports at these points whereby the area of said ports is maintained constant, and discharge ports air and gas izo for the products of combustion separate from the air and gas ports.

13. In an open hearth furnace, a gas port, and an air entrance port, said air entrance 5 port straddling the gas port, water cooling means in the gas port Wall defining bothinner and outer faces of said wall, water cooling means in the wall of the air port substantially opposite the first mentioned lo water cooling means, whereby the area of the air portA is maintained constant, and discharge ports for the products of combusi tion separate from the air and gas ports.

Signed at Pittsburgh, Pennsylvania, this ninth day of May, 1921,

EDWARD J. M GDONNELL. 

